How do I use a FileStream with an IFilePromise without knowing the File?

Question

I've finished the implmentation of my project using Async IFilePromises by extending the ByteArray class. I can drag out of my application and files are created by copying bits over the network, etc. The issue I'm running into is that because I used the ByteArray as my dataprovider, files are stored "In-Memory" until the Close event is fired.
My application routinely copies files around 700 MB and up to 2 GB. The implementation quickly causes out of memory errors. That said, if I change the implementation to use FileStreams then the files are written directly to disk and memory is exactly where I want it to be.
The issue is that the FileStream requires a File object when it's FileStream.open(File, FileMode) method is called. If I manually create a file and use it, then everything is fine, but doing that defeats the purpose of the FilePromise. I lose all the information about where a person dropped the file.
So how do I get access to the File object that is created for each FilePromise? I know one is created by inspecting the call stack when the IFilePromise.open() method is called and inspecting the caller MacFilePromiseWrapper._file.
I've tried simply returning a plain FileStream instead of an extended class in the IFilePromise.open method, but that still gives the same error result when I try to write to the stream (says that the stream isnt open yet).
I would have expected the MacFilePromiseWrapper / FilePromiseWrapper to intelligently handle the returned IDataProvider and perform any "open" and "close" it needed. Please tell me I'm just missing something obvious. I'm so close to being done with this project and I don't want to have to rewrite this using a native implementation. The performance issues (memory usage) will cause me to do just that if I cant figure this out.
Thanks for any help,
Jared

Answer 1

I have resolved the issues myself.
I had the idea of an IFilePromise / IDataInput backwards. The way I thought it worked is that what you were "writing to" when you wrote into a ByteArray and fired of progress events was simply a pipe to a file handle on the disk. That's backwards.  What really happens is that the thing you're writing to is a buffer for the IFilePromise. Firing the open/progress/close events let the file system know that it's safe to pull up to IDataInput.bytesAvailable out of your buffer and write that to the disk and the buffer you write to can be a ByteArray, Socket, FileStream, etc.
The confusion was compounded by my attempts to use FileStream as the IDataInput. What I was doing for "testing purposes" was creating a temporary file and writing my bytes to it. The file handle created by the FilePromise would immediately disappear, so I thought it meant I needed to somehow get access to that handle so I knew where to send my bits using FileStream.open(File, FileMode).
I was really close, but had a mistake in there.  I was on the right track with opening the FileStrea and using the temporary file, but I opened it with the wrong FileMode.
I used FileMode.WRITE because I thought I was writing to the disk only. When I switched it to FileMode.UPDATE (which is read/write) then everything worked as I needed it to.
So to summarize, to use a FileStream as the IDataInput for an IFilePromise you need to:
Create the FileStream object and return it when the IFilePromise.open is called
When you get bytes off your network, etc, dispatch the OPEN event
Open the FileStream object with FileMode.UPDATE and use a temporary file provided by File.createTempFile(), store it for later
Write bytes to the FileStream and send out the proper ProgressEvent.PROGRESS events
Dispatch the COMPLETE event when you're done
the IFilePromise.end() method will be called and you have an opportunity to close your FileStream and to delete the temporary file that was created
I hope this helps someone that runs into a similar issue.